Trim field references in reroute processor (#96941)

Author: felixbarny

docs/changelog/96941.yaml

@@ -0,0 +1,6 @@
+pr: 96941
+summary: Trim field references in reroute processor
+area: Ingest Node
+type: bug
+issues:
+ - 96939

modules/ingest-common/src/main/java/org/elasticsearch/ingest/common/RerouteProcessor.java

@@ -240,6 +240,7 @@ private DataStreamValueSource(String value, Function<String, String> sanitizer)
                 if (fieldReference.startsWith("{") && fieldReference.endsWith("}")) {
                     fieldReference = fieldReference.substring(1, fieldReference.length() - 1);
                 }
+                fieldReference = fieldReference.trim();
                 // only a single field reference is allowed
                 // so something like this is disallowed: {{foo}}-{{bar}}
                 if (fieldReference.contains("{") || fieldReference.contains("}")) {

modules/ingest-common/src/test/java/org/elasticsearch/ingest/common/RerouteProcessorTests.java

@@ -35,7 +35,7 @@ public void testEventDataset() throws Exception {
         IngestDocument ingestDocument = createIngestDocument("logs-generic-default");
         ingestDocument.setFieldValue("event.dataset", "foo");
 
-        RerouteProcessor processor = createRerouteProcessor(List.of("{{event.dataset}}"), List.of());
+        RerouteProcessor processor = createRerouteProcessor(List.of("{{event.dataset }}"), List.of());
         processor.execute(ingestDocument);
         assertDataSetFields(ingestDocument, "logs", "foo", "default");
         assertThat(ingestDocument.getFieldValue("event.dataset", String.class), equalTo("foo"));
@@ -45,7 +45,7 @@ public void testEventDatasetDottedFieldName() throws Exception {
         IngestDocument ingestDocument = createIngestDocument("logs-generic-default");
         ingestDocument.getCtxMap().put("event.dataset", "foo");
 
-        RerouteProcessor processor = createRerouteProcessor(List.of("{{event.dataset}}"), List.of());
+        RerouteProcessor processor = createRerouteProcessor(List.of("{{ event.dataset}}"), List.of());
         processor.execute(ingestDocument);
         assertDataSetFields(ingestDocument, "logs", "foo", "default");
         assertThat(ingestDocument.getCtxMap().get("event.dataset"), equalTo("foo"));
@@ -56,7 +56,7 @@ public void testNoDataset() throws Exception {
         IngestDocument ingestDocument = createIngestDocument("logs-generic-default");
         ingestDocument.setFieldValue("ds", "foo");
 
-        RerouteProcessor processor = createRerouteProcessor(List.of("{{ds}}"), List.of());
+        RerouteProcessor processor = createRerouteProcessor(List.of("{{ ds }}"), List.of());
         processor.execute(ingestDocument);
         assertDataSetFields(ingestDocument, "logs", "foo", "default");
         assertFalse(ingestDocument.hasField("event.dataset"));